The general purpose of this research is to compare the learning of submammalian animals with the learning of mammals, and to relate similarities and differences in the results obtained to similarities and differences in brain structure. The principal subjects are fishes and birds, although there is some work also with amphibians and reptiles as well as with invertebrates, such as worms, mollusks, and arthropods. The principal techniques are behavioral, although neurosurgical, embryological, and biochemical techniques also are employed in the analysis.